The invention relates to home entertainment systems, and to devices for use in such systems. In particular, the present invention relates to so-called home cinema systems comprising at least a television receiver or display screen device coupled with a multiple speaker audio system, as well as to a television receiver for use in such a system.
Home cinema (or home theater) systems allow the user to experience the sound quality of a good cinema set-up in their own home, with a properly set up system creating a 360 degree sound field placing the user in the centre of the action. Home cinema is not just a applicable to films as many television programmes are now broadcast in so-called “surround sound”.
The speaker arrangement for a surround sound system typically comprises a pair of main (left and right) speakers, a centre channel speaker, and a pair of surround speakers; optionally, one or more powered subwoofers may be added for additional bass handling. The main speakers are positioned either side of the screen to allow the audio to move left and right with the image on the screen. The centre channel is particularly for a voice track to a video presentation, such that the characters voices are centred on the screen where they appear. Surround speakers carry ambient audio components of the soundtrack, such as reflections, reverberations and echoes, to enable the user to audibly differentiate the different settings for the displayed scene (e.g. in a small room, or a large hall, or outdoors).
There are currently two principal types of home cinema system, the most popular of which is Dolby Pro-Logic, whilst the newer system is Dolby Digital (also known as AC-3): note that “Dolby”, “Pro-Logic” and “AC-3” are trade marks of Dolby Laboratories, Inc. There are some important differences between these two systems. Dolby Pro-Logic takes an encoded stereo signal and extracts the centre and surround channel signals, whilst Dolby Digital has five discrete digital channels allowing for much greater channel separation with less noise. Also, in Dolby Pro-Logic the surround channel is monophonic and limited in frequency response (100 Hz–7 kHz) whilst for Dolby Digital it is stereo and has a fuller range, providing a significant improvement. Furthermore, Dolby Digital is backwards compatible with any signal source that it is only encoded in Dolby Pro-Logic.
As will be appreciated, the installation of a high-quality surround sound system can be expensive. A further problem is the amount and complexity of cabling involved in connecting up all the speakers, although the problems of high initial outlay and cabling could be reduced for a user if some components could initially or totally be omitted. To these ends, it has been proposed to use the speaker or speakers built in to a television receiver (for stand-alone operation) to carry the centre channel: however, this can lead to control problems for the user, being required to adjust the main and surround channel settings at source, and the centre channel through the television unit controls.